Duct Material Selection

Comparing Duct Material Costs and Long-Term Value

Choosing the right ductwork material is about more than just the upfront cost. While budget is a crucial factor, overlooking long-term value can lead to higher expenses down the road. Comparing duct material costs and long-term value is essential for making an informed decision that balances initial investment with ongoing efficiency and maintenance.


The most common duct materials are galvanized steel, aluminum, and flexible duct. Galvanized steel is the workhorse of the HVAC industry, known for its durability and resistance to leaks. Its a solid choice for a long-lasting system, but the higher initial cost and the potential for rust in damp environments need consideration. Aluminum, while lighter and easier to install, comes with a higher price tag than galvanized steel. However, its inherent resistance to corrosion makes it a good option for humid climates. Flexible duct is the most affordable and easiest to install, making it popular for renovations and tight spaces. However, its corrugated interior can restrict airflow, reducing system efficiency and potentially increasing energy bills over time. Furthermore, its susceptibility to damage and compression can lead to leaks and reduced lifespan compared to rigid ductwork.


Beyond the material itself, installation quality significantly impacts long-term value. Poorly sealed joints, regardless of the material, can lead to energy loss and reduced indoor air quality. Investing in a qualified installer who understands proper sealing techniques is crucial. This upfront cost will pay dividends through lower energy bills and a healthier home environment.


Finally, consider the long-term maintenance requirements of each material. While galvanized steel might require occasional rust treatment, flexible duct may need more frequent inspections and repairs due to its vulnerability to damage. Factoring these potential maintenance costs into your decision can help you avoid unexpected expenses in the future.


In conclusion, choosing the right duct material involves balancing initial costs with long-term value. While flexible duct might seem attractive due to its lower price, the potential for reduced efficiency and increased maintenance could negate those initial savings. Galvanized steel and aluminum offer greater durability and efficiency, but come with a higher upfront cost. By carefully comparing materials and considering installation quality and long-term maintenance, homeowners can make an informed decision that optimizes both their budget and the comfort of their home.

Comparing Duct Material Costs and Long-Term Value

Evaluating Energy Efficiency of Different Duct Materials

Evaluating the energy efficiency of different duct materials is a crucial aspect of duct material selection, directly impacting a buildings HVAC system performance and overall energy consumption. Choosing the right material can significantly reduce energy waste and operational costs, contributing to a more sustainable and economical solution. This evaluation involves considering several key factors.


Firstly, the materials thermal conductivity plays a vital role. Materials with lower thermal conductivity, like fiberglass or insulated flexible ducts, minimize heat transfer between the conditioned air inside the duct and the surrounding environment. This reduces energy loss during both heating and cooling cycles. Conversely, materials with higher conductivity, like uninsulated sheet metal, can lead to significant energy leakage, especially in unconditioned spaces like attics or crawl spaces.


Secondly, airtightness is paramount. Leaky ducts, regardless of the material, can drastically reduce energy efficiency. Air leakage allows conditioned air to escape and unconditioned air to enter, forcing the HVAC system to work harder to maintain the desired temperature. This is especially important for flexible ducts, which can be prone to leaks if not properly installed and sealed. Rigid ducts, like sheet metal, generally offer better airtightness when properly sealed at the joints.


Thirdly, the interior surface of the duct material influences friction and pressure drop. A smooth interior surface, like that found in spiral-wound sheet metal ducts, allows for smoother airflow, reducing the energy required by the fan to move the air. Flexible ducts, while convenient for installation, often have a rougher interior surface, increasing friction and requiring more fan power.


Finally, the climate and the specific application also factor into the energy efficiency equation. In hotter climates, insulation becomes even more critical to minimize heat gain. For example, using insulated flexible ducts or internally lined sheet metal ducts in attic spaces can significantly reduce cooling loads. In colder climates, preventing heat loss is key, making well-sealed and insulated ducts essential.


In conclusion, evaluating the energy efficiency of different duct materials requires a holistic approach, considering thermal conductivity, airtightness, interior surface characteristics, and the specific application and climate. By carefully considering these factors, building owners and HVAC designers can select the most energy-efficient duct material, leading to reduced energy consumption, lower operating costs, and a more environmentally friendly building.

Code Requirements and Local Regulations for Ductwork

Choosing the right duct material isnt just about cost and how easy it is to work with. Its heavily influenced by codes and local regulations, which are put in place to ensure safety, energy efficiency, and proper building performance. These regulations can vary significantly from one area to another, so its crucial to do your homework before making a decision.


Think of it like this: you wouldnt install wood-burning stove without checking local fire codes, right? Ductwork is similar. Codes dictate acceptable materials based on factors like the buildings occupancy (residential, commercial, industrial), the type of HVAC system, and the air being conveyed. For example, flammable materials are generally prohibited in certain applications, and some materials might not be suitable for high-temperature systems.


Local regulations often build upon model codes like the International Mechanical Code (IMC) or the Uniform Mechanical Code (UMC), adding specific requirements based on local climate conditions, environmental concerns, or even historical preservation guidelines. These local amendments can cover everything from allowable duct leakage rates and insulation requirements to fire resistance ratings and even the specific types of sealants and fasteners you can use.


Ignoring these code requirements can lead to several problems. First, it can create safety hazards, like the spread of fire or the release of toxic fumes. Second, it can result in hefty fines and delays in project completion if inspections fail. Finally, using non-compliant materials can impact the efficiency of your HVAC system, leading to higher energy bills and a less comfortable indoor environment.


Therefore, before selecting your duct material, consult with your local building department or a qualified HVAC professional to ensure youre meeting all applicable codes and regulations. It might seem like an extra step, but its a crucial one for ensuring a safe, efficient, and code-compliant HVAC system.

Matching Duct Material to Specific Application Needs

Choosing the right duct material is like picking the right shoes for a job. You wouldnt wear stilettos to a construction site, and you wouldnt wear steel-toed boots to a wedding. Similarly, different ductwork applications demand different materials based on factors like temperature, air pressure, and the environment. Getting it right ensures efficiency, longevity, and safety.


Galvanized steel, the workhorse of the ductwork world, is a popular choice for its strength and affordability. It handles typical heating and cooling applications with ease, standing up to moderate temperatures and pressures. However, in corrosive environments like coastal areas with salty air or industrial settings with chemical fumes, it can rust, leading to leaks and reduced lifespan. For these situations, stainless steel, though pricier, offers superior corrosion resistance, making it a worthwhile investment in the long run.


Aluminum, known for its lightweight nature and excellent formability, shines in applications where flexibility is key. Its easier to install and transport than steel, making it popular for complex ductwork designs. Plus, it resists corrosion naturally, offering a good balance between durability and cost-effectiveness.


Fiberglass duct board, with its inherent insulating properties, is the energy-saving champion. Its construction helps reduce heat transfer, leading to lower energy bills and a quieter system. Its a great option for residential applications, particularly in unconditioned spaces like attics, where minimizing temperature fluctuations is crucial.


Flexible ducts, often made of aluminum or plastic, are the go-to solution for short runs and tight spaces. Their bendable nature allows for easy installation around obstacles, making them ideal for connecting to registers and diffusers. However, their corrugated inner surface creates greater friction, which can reduce airflow and increase energy consumption compared to rigid ducts.


Ultimately, selecting the right duct material is about balancing performance, cost, and longevity. Considering the specific needs of the application, such as the air being conveyed, the surrounding environment, and the budget, will lead to a system that operates efficiently and effectively for years to come.

A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the stack, or chimney effect. The space inside a chimney is called the flue. Chimneys are adjacent to large industrial refineries, fossil fuel combustion facilities or part of buildings, steam locomotives and ships.

In the United States, the term smokestack industry refers to the environmental impacts of burning fossil fuels by industrial society, including the electric industry during its earliest history. The term smokestack (colloquially, stack) is also used when referring to locomotive chimneys or ship chimneys, and the term funnel can also be used.[1][2]

The height of a chimney influences its ability to transfer flue gases to the external environment via stack effect. Additionally, the dispersion of pollutants at higher altitudes can reduce their impact on the immediate surroundings. The dispersion of pollutants over a greater area can reduce their concentrations and facilitate compliance with regulatory limits.

History

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Industrial chimney use dates to the Romans, who drew smoke from their bakeries with tubes embedded in the walls. However, domestic chimneys first appeared in large dwellings in northern Europe in the 12th century. The earliest surviving example of an English chimney is at the keep of Conisbrough Castle in Yorkshire, which dates from 1185 AD,[3] but they did not become common in houses until the 16th and 17th centuries.[4] Smoke hoods were an early method of collecting the smoke into a chimney. These were typically much wider than modern chimneys and started relatively high above the fire, meaning more heat could escape into the room. Because the air going up the shaft was cooler, these could be made of less fireproof materials. Another step in the development of chimneys was the use of built-in ovens which allowed the household to bake at home. Industrial chimneys became common in the late 18th century.

Chimneys in ordinary dwellings were first built of wood and plaster or mud. Since then chimneys have traditionally been built of brick or stone, both in small and large buildings. Early chimneys were of simple brick construction. Later chimneys were constructed by placing the bricks around tile liners. To control downdrafts, venting caps (often called chimney pots) with a variety of designs are sometimes placed on the top of chimneys.

In the 18th and 19th centuries, the methods used to extract lead from its ore produced large amounts of toxic fumes. In the north of England, long near-horizontal chimneys were built, often more than 3 km (2 mi) long, which typically terminated in a short vertical chimney in a remote location where the fumes would cause less harm. Lead and silver deposits formed on the inside of these long chimneys, and periodically workers would be sent along the chimneys to scrape off these valuable deposits.[5]

Construction

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Chimney in NED University

As a result of the limited ability to handle transverse loads with brick, chimneys in houses were often built in a "stack", with a fireplace on each floor of the house sharing a single chimney, often with such a stack at the front and back of the house. Today's central heating systems have made chimney placement less critical, and the use of non-structural gas vent pipe allows a flue gas conduit to be installed around obstructions and through walls.

Chimney in North London
Flue

Most modern high-efficiency heating appliances do not require a chimney. Such appliances are generally installed near an external wall, and a noncombustible wall thimble[clarification needed] allows a vent pipe to run directly through the external wall.

On a pitched roof where a chimney penetrates a roof, flashing is used to seal up the joints. The down-slope piece is called an apron, the sides receive step flashing and a cricket is used to divert water around the upper side of the chimney underneath the flashing.[6]

Industrial chimneys are commonly referred to as flue-gas stacks and are generally external structures, as opposed to those built into the wall of a building. They are generally located adjacent to a steam-generating boiler or industrial furnace and the gases are carried to them with ductwork. Today the use of reinforced concrete has almost entirely replaced brick as a structural element in the construction of industrial chimneys. Refractory bricks are often used as a lining, particularly if the type of fuel being burned generates flue gases containing acids. Modern industrial chimneys sometimes consist of a concrete windshield with a number of flues on the inside.

The 300 m (980 ft) high steam plant chimney at the Secunda CTL's synthetic fuel plant in Secunda, South Africa consists of a 26 m (85 ft) diameter windshield with four 4.6 metre diameter concrete flues which are lined with refractory bricks built on rings of corbels spaced at 10 metre intervals. The reinforced concrete can be cast by conventional formwork or sliding formwork. The height is to ensure the pollutants are dispersed over a wider area to meet legal or other safety requirements.

Residential flue liners

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A flue liner is a secondary barrier in a chimney that protects the masonry from the acidic products of combustion, helps prevent flue gas from entering the house, and reduces the size of an oversized flue. Since the 1950s, building codes in many locations require newly built chimneys to have a flue liner. Chimneys built without a liner can usually have a liner added, but the type of liner needs to match the type of appliance it services. Flue liners may be clay or concrete tile, metal, or poured in place concrete.

Clay tile flue liners are very common in the United States, although it is the only liner that does not meet Underwriters Laboratories 1777 approval and frequently they have problems such as cracked tiles and improper installation.[7] Clay tiles are usually about 2 feet (0.61 m) long, available in various sizes and shapes, and are installed in new construction as the chimney is built. A refractory cement is used between each tile.

Metal liners may be stainless steel, aluminum, or galvanized iron and may be flexible or rigid pipes. Stainless steel is made in several types and thicknesses. Type 304 is used with firewood, wood pellet fuel, and non-condensing oil appliances, types 316 and 321 with coal, and type AL 29-4C is used with high efficiency condensing gas appliances. Stainless steel liners must have a cap and be insulated if they service solid fuel appliances, but following the manufacturer's instructions carefully.[7] Aluminum and galvanized steel chimneys are known as class A and class B chimneys. Class A are either an insulated, double wall stainless steel pipe or triple wall, air-insulated pipe often known by its genericized trade name Metalbestos. Class B are uninsulated double wall pipes often called B-vent, and are only used to vent non-condensing gas appliances. These may have an aluminum inside layer and galvanized steel outside layer.

Concrete flue liners are like clay liners but are made of a refractory cement and are more durable than the clay liners.

Poured in place concrete liners are made by pouring special concrete into the existing chimney with a form. These liners are highly durable, work with any heating appliance, and can reinforce a weak chimney, but they are irreversible.

Chimney pots, caps, and tops

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A chimney pot is placed on top of the chimney to expand the length of the chimney inexpensively, and to improve the chimney's draft. A chimney with more than one pot on it indicates that multiple fireplaces on different floors share the chimney.

A cowl is placed on top of the chimney to prevent birds and other animals from nesting in the chimney. They often feature a rain guard to prevent rain or snow from going down the chimney. A metal wire mesh is often used as a spark arrestor to minimize burning debris from rising out of the chimney and making it onto the roof. Although the masonry inside the chimney can absorb a large amount of moisture which later evaporates, rainwater can collect at the base of the chimney. Sometimes weep holes are placed at the bottom of the chimney to drain out collected water.

A chimney cowl or wind directional cap is a helmet-shaped chimney cap that rotates to align with the wind and prevent a downdraft of smoke and wind down the chimney.

An H-style cap is a chimney top constructed from chimney pipes shaped like the letter H. It is an age-old method of regulating draft in situations where prevailing winds or turbulences cause downdraft and back-puffing. Although the H cap has a distinct advantage over most other downdraft caps, it fell out of favor because of its bulky design. It is found mostly in marine use but has been regaining popularity due to its energy-saving functionality. The H-cap stabilizes the draft rather than increasing it. Other downdraft caps are based on the Venturi effect, solving downdraft problems by increasing the updraft constantly resulting in much higher fuel consumption.

A chimney damper is a metal plate that can be positioned to close off the chimney when not in use and prevent outside air from entering the interior space, and can be opened to permit hot gases to exhaust when a fire is burning. A top damper or cap damper is a metal spring door placed at the top of the chimney with a long metal chain that allows one to open and close the damper from the fireplace. A throat damper is a metal plate at the base of the chimney, just above the firebox, that can be opened and closed by a lever, gear, or chain to seal off the fireplace from the chimney. The advantage of a top damper is the tight weatherproof seal that it provides when closed, which prevents cold outside air from flowing down the chimney and into the living space—a feature that can rarely be matched by the metal-on-metal seal afforded by a throat damper. Additionally, because the throat damper is subjected to intense heat from the fire directly below, it is common for the metal to become warped over time, thus further degrading the ability of the throat damper to seal. However, the advantage of a throat damper is that it seals off the living space from the air mass in the chimney, which, especially for chimneys positioned on an outside of wall of the home, is generally very cold. It is possible in practice to use both a top damper and a throat damper to obtain the benefits of both. The two top damper designs currently on the market are the Lyemance (pivoting door) and the Lock Top (translating door).

In the late Middle Ages in Western Europe the design of stepped gables arose to allow maintenance access to the chimney top, especially for tall structures such as castles and great manor houses.

Chimney draught or draft

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When coal, oil, natural gas, wood, or any other fuel is combusted in a stove, oven, fireplace, hot water boiler, or industrial furnace, the hot combustion product gases that are formed are called flue gases. Those gases are generally exhausted to the ambient outside air through chimneys or industrial flue-gas stacks (sometimes referred to as smokestacks).

The combustion flue gases inside the chimneys or stacks are much hotter than the ambient outside air and therefore less dense than the ambient air. That causes the bottom of the vertical column of hot flue gas to have a lower pressure than the pressure at the bottom of a corresponding column of outside air. That higher pressure outside the chimney is the driving force that moves the required combustion air into the combustion zone and also moves the flue gas up and out of the chimney. That movement or flow of combustion air and flue gas is called "natural draught/draft", "natural ventilation", "chimney effect", or "stack effect". The taller the stack, the more draught or draft is created. There can be cases of diminishing returns: if a stack is overly tall in relation to the heat being sent out of the stack, the flue gases may cool before reaching the top of the chimney. This condition can result in poor drafting, and in the case of wood burning appliances, the cooling of the gases before emission can cause creosote to condense near the top of the chimney. The creosote can restrict the exit of flue gases and may pose a fire hazard.

Designing chimneys and stacks to provide the correct amount of natural draft involves a number of design factors, many of which require iterative trial-and-error methods.

As a "first guess" approximation, the following equation can be used to estimate the natural draught/draft flow rate by assuming that the molecular mass (i.e., molecular weight) of the flue gas and the external air are equal and that the frictional pressure and heat losses are negligible: where:

  • Q = chimney draught/draft flow rate, m3/s
  • A = cross-sectional area of chimney, m2 (assuming it has a constant cross-section)
  • C = discharge coefficient (usually taken to be from 0.65 to 0.70)
  • g = gravitational acceleration, 9.807 m/s2
  • H = height of chimney, m
  • Ti = average temperature inside the chimney, K
  • Te = external air temperature, K.

Combining two flows into chimney: At+Af<A, where At=7.1 inch2 is the minimum required flow area from water heater tank and Af=19.6 inch2 is the minimum flow area from a furnace of a central heating system.

Draft hood

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Gas fired appliances must have a draft hood to cool combustion products entering the chimney and prevent updrafts or downdrafts.[8][9][10]

Maintenance and problems

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A characteristic problem of chimneys is they develop deposits of creosote on the walls of the structure when used with wood as a fuel. Deposits of this substance can interfere with the airflow and more importantly, they are combustible and can cause dangerous chimney fires if the deposits ignite in the chimney.

Heaters that burn natural gas drastically reduce the amount of creosote buildup due to natural gas burning much cleaner and more efficiently than traditional solid fuels. While in most cases there is no need to clean a gas chimney on an annual basis that does not mean that other parts of the chimney cannot fall into disrepair. Disconnected or loose chimney fittings caused by corrosion over time can pose serious dangers for residents due to leakage of carbon monoxide into the home.[11] Thus, it is recommended—and in some countries even mandatory—that chimneys be inspected annually and cleaned on a regular basis to prevent these problems. The workers who perform this task are called chimney sweeps or steeplejacks. This work used to be done largely by child labour and, as such, features in Victorian literature. In the Middle Ages in some parts of Europe, a stepped gable design was developed, partly to provide access to chimneys without use of ladders.

Masonry (brick) chimneys have also proven to be particularly prone to crumbling during earthquakes. Government housing authorities in cities prone to earthquakes such as San Francisco, Los Angeles, and San Diego now recommend building new homes with stud-framed chimneys around a metal flue. Bracing or strapping old masonry chimneys has not proven to be very effective in preventing damage or injury from earthquakes. It is now possible to buy "faux-brick" facades to cover these modern chimney structures.

Other potential problems include:

  • "spalling" brick, in which moisture seeps into the brick and then freezes, cracking and flaking the brick and loosening mortar seals.
  • shifting foundations, which may degrade integrity of chimney masonry
  • nesting or infestation by unwanted animals such as squirrels, racoons, or chimney swifts
  • chimney leaks
  • drafting issues, which may allow smoke inside building[12]
  • issues with fireplace or heating appliance may cause unwanted degradation or hazards to chimney

Chimneys of special interest

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Chimneys with observation decks

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Several chimneys with observation decks were built. The following possibly incomplete list shows them.

Name Country Town Coordinates Year of completion Total height Height of observation deck Remarks
Chimney of Beitou Refuse Incineration Plant Taiwan Teipei 25°06′29″N 121°29′58″E / 25.108043°N 121.499384°E / 25.108043; 121.499384 (Chimney of Beitou Refuse Incineration Plant) 2000 150 m (492 ft) 116 m (381 ft) revolving restaurant in a height of 120 metres (394 ft)
Radio City Tower United Kingdom Liverpool   53°24′23″N 2°58′55″W / 53.406332°N 2.982002°W / 53.406332; -2.982002 (Radio City Tower) 1971 148 m (486 ft) 124.7 m (409 ft) chimney for the heating system of a nearby mall
Large Chimney of Warsaw Refuse Incineration Plant Poland Warsaw   52°15′41″N 21°06′18″E / 52.261448°N 21.105072°E / 52.261448; 21.105072 (Large Chimney of Warsaw Refuse Incineration Plant) 2024 72 m (236 ft)   observation deck only accessible at guided tours through the facility
Bernard Brewery Chimney Czech Humpolec   49°32′23″N 15°21′36″E / 49.539786°N 15.360043°E / 49.539786; 15.360043 (Bernard Brewery Chimney)   40.7 m (134 ft) 33 m (108 ft) observation deck added in 2020/21
Dům DÄ›tí a Mládeže v ModÃ…â„¢anech Czech Prague   50°00′44″N 14°24′49″E / 50.012154°N 14.413657°E / 50.012154; 14.413657 (Dům DÄ›tí a Mládeže v ModÃ…â„¢anech) 2004 15 m (49 ft) 12 m (39 ft) observation platform on chimney of the roof of a youth centre
Chimney of Zenner Heating Building Germany Berlin   52°29′17″N 13°28′38″E / 52.488097°N 13.477282°E / 52.488097; 13.477282 (Chimney of Zenner Heating Building) 1955 15 m (49 ft) 12 m (39 ft) perhaps never in use as observation tower

Chimneys used as electricity pylon

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At several thermal power stations at least one smokestack is used as electricity pylon. The following possibly incomplete list shows them.

Country City Coordinates Name Height Year of construction Voltage Remarks
Germany Gelsenkirchen   51°36′02″N 7°00′16″E / 51.600623°N 7.004573°E / 51.600623; 7.004573 (Scholven Power Station, Chimney for Units B, C, D and E) Scholven Power Station, Chimney for Units B, C, D and E 300 m   220 kV  
Belarus Novolukoml   54°40′45″N 29°08′09″E / 54.679048°N 29.135925°E / 54.679048; 29.135925 (Lukoml Power Station, Chimney 1) Lukoml Power Station, Chimney 1 250 m 1969 330 kV  
Belarus Novolukoml   54°40′48″N 29°08′07″E / 54.679941°N 29.135259°E / 54.679941; 29.135259 (Lukoml Power Station, Chimney 2) Lukoml Power Station, Chimney 2 250 m 1971 330 kV  
Belarus Novolukoml   54°40′53″N 29°08′04″E / 54.681290°N 29.134428°E / 54.681290; 29.134428 (Lukoml Power Station, Chimney 3) Lukoml Power Station, Chimney 3 250 m 1973 330 kV  
Lithuania Elektrenai   54°46′17″N 24°38′50″E / 54.771463°N 24.647291°E / 54.771463; 24.647291 (ElektrÄ—nai Power Plant, Chimney 1) ElektrÄ—nai Power Plant, Chimney 1 150 m   330 kV dismantled
Lithuania Elektrenai   54°46′12″N 24°38′48″E / 54.770110°N 24.646765°E / 54.770110; 24.646765 (ElektrÄ—nai Power Plant, Chimney 2) ElektrÄ—nai Power Plant, Chimney 2 250 m   330 kV dismantled
Moldova Dnestrovsc   46°37′40″N 29°56′23″E / 46.627864°N 29.939691°E / 46.627864; 29.939691 (Cuciurgan power station, Chimney 1) Cuciurgan power station, Chimney 1 180 m 1964 110 kV  
Moldova Dnestrovsc   46°37′44″N 29°56′23″E / 46.628880°N 29.939622°E / 46.628880; 29.939622 (Cuciurgan power station, Chimney 2) Cuciurgan power station, Chimney 2 180 m 1966 330 kV  
Moldova Dnestrovsc   46°37′49″N 29°56′23″E / 46.630199°N 29.939622°E / 46.630199; 29.939622 (Cuciurgan power station, Chimney 3) Cuciurgan power station, Chimney 3 180 m 1971 330 kV  
Russia Archangelsk   64°34′29″N 40°34′24″E / 64.574788°N 40.573261°E / 64.574788; 40.573261 (Archangelsk Cogeneration Plant, Chimney 1) Archangelsk Cogeneration Plant, Chimney 1 170 m   220 kV  
Russia Saint Petersburg   59°58′14″N 30°22′35″E / 59.970595°N 30.376425°E / 59.970595; 30.376425 (Vyborgskaya Cogenaration Plant, Chimney 1) Vyborgskaya Cogenaration Plant, Chimney 1 120 m   110 kV  
Russia Tobolsk   58°14′44″N 68°26′43″E / 58.245439°N 68.445224°E / 58.245439; 68.445224 (Tobolsk Cogeneration Plant, Chimney 1) TEC Tobolsk, Chimney 1 240 m 1980 110 kV  
Russia Tobolsk   58°14′45″N 68°26′55″E / 58.245781°N 68.448590°E / 58.245781; 68.448590 (Tobolsk Cogeneration Plant, Chimney 2) TEC Tobolsk, Chimney 2 270 m 1986 220 kV  
Russia Kashira   54°51′24″N 38°15′23″E / 54.856639°N 38.256428°E / 54.856639; 38.256428 (Kashira Power Plant, Chimney 1) Kashira Power Plant, Chimney 1 250 m 1966 220 kV  
Russia Energetik   51°45′12″N 58°48′09″E / 51.753324°N 58.802583°E / 51.753324; 58.802583 (Iriklinskaya Power Station, Chimney 1) Iriklinskaya Power Station, Chimney 1 180 m   220 kV  
Russia Energetik   51°45′12″N 58°48′14″E / 51.753453°N 58.803983°E / 51.753453; 58.803983 (Iriklinskaya Power Station, Chimney 2) Iriklinskaya Power Station, Chimney 2 180 m   220 kV  
Russia Energetik   51°45′13″N 58°48′22″E / 51.753483°N 58.806183°E / 51.753483; 58.806183 (Iriklinskaya Power Station, Chimney 3) Iriklinskaya Power Station, Chimney 3 250 m   500 kV  
Russia Konakovo   56°44′23″N 36°46′22″E / 56.739703°N 36.772833°E / 56.739703; 36.772833 (Konakovo Power Station, Chimney 1) Konakovo Power Station, Chimney 1 180 m 1964 220 kV  
Russia Konakovo   56°44′26″N 36°46′20″E / 56.740627°N 36.772308°E / 56.740627; 36.772308 (Konakovo Power Station, Chimney 2) Konakovo Power Station, Chimney 2 180 m 1966 220 kV  
Russia Koryazhma   61°18′09″N 47°07′13″E / 61.302456°N 47.120396°E / 61.302456; 47.120396 (Chimney 1 of Cogenaration Plant 1 of Kotlas Pulp and Paper Mill) Chimney 1 of Cogenaration Plant 1 of Kotlas Pulp and Paper Mill 105 m 1961 220 kV  
Ukraine Burshtyn   49°12′27″N 24°40′03″E / 49.207578°N 24.667450°E / 49.207578; 24.667450 (Burshtyn Power Station, Chimney 1) Burshtyn Power Station, Chimney 1 180 m 1965 330 kV  
Ukraine Burshtyn   49°12′31″N 24°39′57″E / 49.208595°N 24.665921°E / 49.208595; 24.665921 (Burshtyn Power Station, Chimney 2) Burshtyn Power Station, Chimney 2 250 m 1966 330 kV  
Ukraine Burshtyn   49°12′34″N 24°39′54″E / 49.209334°N 24.664918°E / 49.209334; 24.664918 (Burshtyn Power Station, Chimney 3) Burshtyn Power Station, Chimney 3 250 m 1966 330 kV  
Ukraine Trypillia   50°08′01″N 30°44′52″E / 50.133591°N 30.747659°E / 50.133591; 30.747659 (Trypillia Power Station, Chimney 1) Trypillia Power Station, Chimney 1 180 m 1968 330 kV  
Ukraine Trypillia   50°08′00″N 30°44′44″E / 50.133239°N 30.745553°E / 50.133239; 30.745553 (Trypillia Power Station, Chimney 2) Trypillia Power Station, Chimney 2 180 m 1972 330 kV  

Nearly all this structures exist in an area, which was once part of the Soviet Union. Although this use has the disadvantage that conductor ropes may corrode faster due to the exhaust gases, one can find such structures also sometimes in countries not influenced by the former Soviet Union. An example herefore is one chimney of Scholven Power Plant in Gelsenkirchen, which carries one circuit of an outgoing 220 kV-line.

Chimneys used as water tower

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Chimneys can also carry a water tank on their structure. This combination has the advantage that the warm smoke running through the chimney prevents the water in the tank from freezing. Before World War II such structures were not uncommon, especially in countries influenced by Germany.

Chimneys used as radio tower

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Chimneys can carry antennas for radio relay services, cell phone transmissions, FM-radio and TV on their structure. Also long wire antennas for mediumwave transmissions can be fixed at chimneys. In all cases it had to be considered that these objects can easily corrode especially when placed near the exhaust. Sometimes chimneys were converted into radio towers and are not useable as ventilation structure any more.

Chimneys used for advertising

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As chimneys are often the tallest part of a factory, they offer the possibility as advertising billboard either by writing the name of the company to which they belong on the shaft or by installing advertisement boards on their structure.

Cooling tower used as an industrial chimney

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At some power stations, which are equipped with plants for the removal of sulfur dioxide and nitrogen oxides, it is possible to use the cooling tower as a chimney. Such cooling towers can be seen in Germany at the Großkrotzenburg Power Station and at the Rostock Power Station. At power stations that are not equipped for removing sulfur dioxide, such usage of cooling towers could result in serious corrosion problems which are not easy to prevent.

See also

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References

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  1. ^ C.F. Saunders (1923), The Southern Sierras of California
  2. ^ "Jules Verne (1872), Around the World in Eighty Days". Retrieved 2006-07-30.
  3. ^ James Burke, Connections (Little, Brown and Co.) 1978/1995, ISBN 0-316-11672-6, p. 159
  4. ^ Sparrow, Walter Shaw. The English house: how to judge its periods and styles. London: Eveleigh Nash, 1908. 85–86.
  5. ^ "Lead Mining". The Northern Echo. Newsquest Media Group. Retrieved 10 April 2012.
  6. ^ Roofing, flashing & waterproofing. Newtown, CT: Taunton Press, 2005. 43–50.
  7. ^ a b Bliss, Stephen, ed.. Troubleshooting guide to residential construction: the diagnosis and prevention of common building problems. Richmond, VT: Builderburg Group, 1997. 197. Print.
  8. ^ "Field Installation of Draft Hoods" (PDF). A.O. Smith Water Products Company. 2009. Retrieved January 6, 2016.
  9. ^ "Guide to Draft Hoods on Gas Fired Heating Equipment". InspectApedia.com. 2017. Retrieved January 6, 2016.
  10. ^ Reuben Saltzman (September 24, 2013). "Water Heater Backdrafting, Part 1 of 2: Why it Matters and What to Look For". Structure Tech. Retrieved January 6, 2016.
  11. ^ Chimney Problems and Warnings Signs
  12. ^ "Chimney Airflow Problems". 8 June 2022.
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Industrial exhaust ducts are pipe systems that connect hoods to industrial chimneys through other components of exhaust systems like fans, collectors, etc. Ducts are low-pressure pneumatic conveyors to convey dust, particles, shavings, fumes, or chemical hazardous components from air in the vicinity to a shop floor or any other specific locations like tanks, sanding machines, or laboratory hoods. Ducts can be fabricated from a variety of materials including carbon steel, stainless steel, PVC, and fiberglass. [1] They can be fabricated through rolling (preferable for ducts of 12" or more in diameter) or extruded (for ducts up to 18").[2]

HVAC systems do not include this category of industrial application, namely exhaust systems. A distinction from HVAC system ducts is that the fluid (air) conveyed through the duct system may not be homogeneous. An industrial exhaust duct system is primarily a pneumatic conveying system and is basically governed by laws of flow of fluids.[3]

Fluid flow

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The conveying fluid that flows through the duct system is air. Air transports materials from the hood to a destination. It is also instrumental in capturing the material into the flow system. Air is a compressible fluid, but for engineering calculations, air is considered as incompressible as a simplification, without any significant errors.

Design

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Process design of exhaust system will include

  • Identification of contaminants, their density and size
  • Deciding of air flow
  • Sizing of the ductwork
  • Calculation of resistance
  • Finalizing the capacity of blower, etc.[4]

The goal is to keep contaminants out using minimum airflow. It is estimated that increase in an inch wg[clarification needed] of static pressure can add a few thousands of dollars to the operation cost per annum.

See also

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References

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  1. ^ Duct Work Assembly Archived 2020-02-24 at the Wayback Machine U.S. Bellows, (retrieved May 2012)
  2. ^ KCH Engineered Systems
  3. ^ [1] Archived 2015-09-19 at the Wayback Machine ASHRAE Technical Committee 5.2 - Duct Design
  4. ^ [2] Archived 2017-02-20 at the Wayback Machine Industrial Duct System Design Fundamentals

The word duct is derived from the Latin word for led/leading. It may refer to:

  • Duct (anatomy), various ducts in anatomy and physiology
  • Duct (HVAC), for transfer of air between spaces in a structure
  • Duct tape, a kind of adhesive tape
  • Ducted fan, motor for aircraft
  • Electrical bus duct, a metal enclosure for busbars
  • Duct (industrial exhaust), industrial exhaust duct system designed for low pressure-pneumatic convey of gas, fumes, dusts, shavings, and other pollutants from works space to atmosphere after cleaning and removal of contaminants
  • Atmospheric duct, a horizontal layer in the lower atmosphere in which the vertical refractive index gradients are such that radio signals (a) are guided or ducted, (b) tend to follow the curvature of the Earth, and (c) experience less attenuation in the ducts than they would if the ducts were not present
  • Surface duct, a sound propagation phenomenon at sea
  • Duct Publishing, an imprint of the German group VDM Publishing devoted to the reproduction of Wikipedia content
  • Dispatchable Unit Control Table (DUCT) in z/Architecture
  • Flexible Ducting

See also

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The best duct material depends on factors like your local climate (humidity, temperature swings), your budget, and the specific application. Common options include galvanized steel, flexible ductwork, and fiberglass duct board, each with varying cost and performance characteristics.
Proper sizing and sealing are critical for efficient airflow and energy savings. A qualified HVAC technician should perform a Manual J calculation (load calculation) to determine the correct duct size and ensure all joints and connections are properly sealed to prevent leaks.
Different duct materials require different maintenance. Flexible ductwork may require more frequent cleaning and inspection due to its susceptibility to accumulating dust and debris. Rigid ductwork like galvanized steel typically requires less maintenance.